The present invention is directed to a practical, low cost, reusable Self Supporting Riser (SSR) made from modular tubular joints and specialty joints that can be assembled and reassembled interchangeably for different locations and applications. Further, the present invention is directed to the interface between an SSR and a vessel subject to relatively high motions in all 6 degrees of freedom, including heave, pitch, and roll motions, for downhole work in a well through the SSR.
The concept of a free standing or self supporting riser is known and has been used as an aid to offshore production from oil wells. A prior art SSR typically consists of as a minimum: an anchor or infrastructure connection location on the seafloor, pipe joints, buoyancy, and interfaces for use. Previous SSRs were typically designed with emphasis on the installed function of the riser and little attention was normally given to installation and even less consideration to removal of the riser.
Downhole intervention in deep water satellite hydrocarbon wells has been done primarily by a Mobile Offshore Drilling Unit (MODU) with capability to deploy a vessel supported riser and deploy drill pipe through the riser and down into the well. A satellite well is one that can not be vertically accessed from a fixed or moored surface production facility. A MODU is a large, high cost, multipurpose vessel which frequently can not be economically justified, given the limited additional product that can be recovered from a partially depleted reservoir.